1. Field of the Invention
The present invention relates to an edible dispersion comprising an aqueous phase and a fat phase, the composition constituting the aqueous phase being a gel-forming composition, and to a process for the preparation thereof.
2. The Related Art
In edible dispersions comprising a fat phase and an aqueous phase, such as, for example, margarine, mayonnaise and bread spread, the composition that constitutes the aqueous phase often is a gel-forming composition. For various reasons, for example to obtain good in-mouth properties, it can be desirable to employ an aqueous phase composition that forms a gel having a relatively low melting point. The gelling agent commonly used for this purpose is gelatin. With gelatin, aqueous gels can be made that usually have a melting point of about 30.degree.-35.degree. C. Gelatin can be used to prepare very weak gels but, alternatively, rather firm gels can suitably be obtained with gelatin as well. For example, the gel strength of aqueous gelatin gels, as indicated by the yield stress at 5.degree. C., may range from about 0.1 kN/m.sup.2 to about 200 kN/m.sup.2 Gelatin gels usually are rather elastic. However, the use of gelatin is not without disadvantages. For example, gelatin is a rather expensive gelling agent. Also, the gelatin gel sets rather slowly, which can be undesirable. Despite these disadvantages, however, a commercially acceptable gelling agent that provides relatively low melting gels and that can be used in the composition that is to constitute the aqueous phase of edible dispersions, as an alternative to gelatin, has never been found.
Kappa- and iota-carrageenan are well-known polysaccharide gelling agents. However, gels prepared with commonly available carrageenan compositions have high melting points. The gel melting point of aqueous phase compositions comprising carrageenan is often as high as 55.degree. C. or even higher. This is considered undesirable because it prevents the edible dispersion from breaking down rapidly and releasing its flavour in the mouth. Moreover, carrageenan gels commonly set very rapidly. Consequently, when using an aqueous phase composition comprising carrageenan as gelling agent, the gel tends to set early in the production process, which can give rise to very high line pressures. Because of these disadvantages, in practice carrageenan is only used to a limited extent as gelling agent in aqueous phase compositions for the preparation of edible dispersions.
The melting point of a gel is the temperature at which the gel network structure disappears if the gel is heated slowly. However, in practice it is difficult to determine this temperature accurately and reliably, and it is therefore common practice to refer to the closely related transition midpoint temperature Tm, which is determined by means of optical rotation dispersion (ORD). The Tm-value of carrageenan gels commonly lies within the experimental error range of the gel melting point. However, the Tm determination via ORD depends on the transition from the ordered to the disordered state. The ordered state may be a gel, but this need not be so. Aqueous carrageenan systems may also occur in the so-called double helix state. In this state, it is believed, pairs of polymer molecules have formed, presumably in a double helix conformation, which is indicated by the ORD measurement as an ordered state, but microscopically the system is still a pourable liquid, because no wide-ranging three-dimensional network has formed. Thus, for carrageenan gels the Tm-value usually does not differ substantially from the gel melting point. However, the fact that the midpoint temperature for the order to disorder transition, Tm, can be determined does not imply that the system at the lower temperature is a gel; the ordered state may also be the non-gelled, double helix state.
Although in practice the Tm-value of a carrageenan gel is often used interchangeably with the temperature at which the gel melts, which is correct for the majority of carrageenan gels, substantial differences between the temperature at which a gel comprising carrageenan melts and the Tm-value of that gel may occur. If, for example, in a carrageenan gel composition that has a Tm value and a gel melting point of about 50.degree. C., locust bean gum is incorporated, this can cause an increase of the temperature at which the gel melts to e.g. about 55.degree. C. or 60.degree. C. without changing the Tm value of the order to disorder transition. For the large majority of carrageenan gels, however, the gel melting point does not differ substantially from the Tm value.
It is well known that the properties of aqueous carrageenan systems may vary substantially in dependence of the type and quantity of ions contained in the system. For example, it is known that the solubility of carrageenan gelling agent in an aqueous medium and the elasticity and the Tm value of the carrageenan gel can be varied by changing the ionic environment. However, as described above, the known gel-forming carrageenan compositions, suitable to be used as aqueous phase composition of an edible dispersion, have undesirably high Tm-values.